Multi-Party Quantum Communication Possible

Physicists at the Institute for Quantum Computing at the University of Waterloo have demonstrated distributed communication between three entangled photons, at three different locations. The locations, designated as Alice, Bob, and Charlie in the picture below, are several hundreds of meters apart. This experiment proves quantum nonlocality for more than two entangled photons (see the figure below):

The experiment demonstrated the distribution of three entangled particles, which can eventually be used to do more than pairwise communication where only one party can communicate with another. It opens the possibility for multipartite quantum communication protocols, including Quantum Key Distribution (QKD), third man cryptography, and quantum secret sharing.

“The interesting result is that we now have the ability to do more than paired quantum communication,” said the paper’s lead author Chris Erven, a former IQC PhD student who is now a research assistant at the University of Bristol.

“QKD, so far, has been a pairwise system — meaning that it works best and with less assumptions when you’re only talking with one other person. This is the first experiment where you can now imagine a network of people connected in different ways using the correlations between three or more photons.”

As soon as I heard about this successful experiment, I knew I had heard about this kind of communication system before. In James Blish's 1954 story, he introduces the idea of a Dirac Transmitter; the quote below comes from his 1957 novels combined as Cities in Flight. The Dirac transmitter is a multi-party communication system that allows instantaneous communication across the universe:

...one of the things they offer in payment is a new course which they say will take us into an iron-bearing star cluster, very recently settled, where there's likely to be plenty of work for us."

"So they say."

"...and I belive them," Lutz said sharply. "Everything they've said to me, they've also said on the open air, by Dirac transmitter. The cops have heard every word, not only locally, but wherever in the whole universe that there's a Dirac transceiver."